Various powders exemplified by white and colored pigments such as titanium oxide, zinc oxide, red iron oxide, and the like and extender pigments such as mica, sericite, and the like are widely used in the fields of basic cosmetic compositions and other various cosmetic compositions such as sunscreens, nail colors, nail coats, foundations, mascaras, eye liners, and the like. However, untreated powder is prone to agglomerate due to the electric charge and polarity, trace amount of impurities, and the like on the powder surface. Therefore, powders that have been subject to various surface treatments are widely used for the purpose of enhancing dispersibility and stability of a powder in a cosmetic composition and also improving the tactile sensation, moisture resistance, sebum resistance, and the like of a cosmetic composition comprising a powder.
Known examples of such surface treatments include lipophilization treatments using an oil agent, a metal soap, or the like; hydrophilization treatments using a surfactant, water-soluble polymer, or the like; hydrophobization treatments using silicone compounds; silica treatments; alumina treatments; and the like. Particularly, in recent years, there have been many cases where a surface treatment using a silicone compound having a reactive moiety in the molecule have been performed. The reactive moiety forms a chemical bond with the powder surface and, as a result, the surface treatment using the silicone compound is effective from the perspective of simultaneously modifying the surface of the powder and blocking the surface activity of the powder. Additionally, because surface treatment can be thoroughly performed, the surface treatment agent will not separate from the powder surface, even when compounded in a cosmetic composition comprising a solvent. Moreover, changes in properties of the powder due to the surface treatment can be kept to a minimum. An example of such a surface treatment is a method in which a powder is surface treated using a methylhydrogenpolysiloxane (Patent Document 1). However, in this method, unreacted Si—H groups still remain even after the surface treating of the powder and, therefore, there is a problem when this powder is compounded in a cosmetic composition because hydrogen gas may be produced depending on the components and the like in the cosmetic composition.
On the other hand, methods for manufacturing a powder dispersion using a hydrophilic modified organopolysiloxane that has good compatibility with the powder surface have been proposed. Examples thereof include a method for forming a polyether-modified organopolysiloxane into a powder dispersing aid (Patent Document 2) and a method for forming an organopolysiloxane modified by polyglycerine or a similar polyhydric alcohol into a powder dispersing aid (Patent Document 3). However, there are problems in that the powder dispersion effectiveness is still insufficient, viscosity of a power dispersion obtained by dispersing a powder in silicone oil or a similar oil agent increases gradually over time, fluidity is lost, and the like.
As a method to resolve the problems described above, the present applicant has proposed methods using a co-modified organopolysiloxane copolymer having a group that has a carbosiloxy dendron structure and a glycerin derivative, polyhydric alcohol, or similar hydrophilic group in the molecule (Patent Documents 4, 5, 6, and 7). Such co-modified organopolysiloxanes are safe and do not produce hydrogen, and can be advantageously used in the surface treating of a powder. Moreover, affinity with other raw materials of cosmetic compositions is superior, and the dispersibility and stability of the powder in a cosmetic composition comprising a powder can be enhanced.
However, although the co-modified organopolysiloxane copolymers disclosed in Patent Documents 4 to 7 are outstanding from the perspective of performance, polyglycerine groups, xylitol groups, and the like are problematic in that they are relatively expensive to produce, which has a substantial cost impact on the final product. Therefore, there is a demand for a surface treatment agent, a cosmetic raw material, and a cosmetic containing the same which have surface treatment performance equal or superior to that of these co-modified organopolysiloxane copolymers and can be produced at low cost.
On the other hand, organopolysiloxanes having modified groups containing saccharide components consisting of saccharides and sugar derivatives in the molecule, reactions for obtaining the organopolysiloxanes, and the use thereof in cosmetics have long been known (for example, Patent Documents 8 to 13). Since these modified groups containing saccharide components can be synthesized with a simple method using simple amino-modified silicone and inexpensive sugar lactones, the cost is low, and a wide variety of sugar-modified silicones can be derived by using various sugar lactones. However, the applications thereof are still limited, and the substances have only been used as certain types of surfactants such as surface treatment agents or gelling agents. In addition, there are problems in that the performance as a surface treatment agent is still insufficient, and the viscosity of a powder dispersion obtained by dispersing a powder in an oil agent such as silicone oil increases gradually over time, which leads to a loss of fluidity. Further, in these references, there is no disclosure of a co-modified organopolysiloxane having a modified group containing a saccharide component as a functional group independent of a siloxane dendron structure in the molecule, and in particular, there is no disclosure that the molecular chain length or modification rate is selected in order to improve the surface treatment performance.
The present applicants have proposed an organopolysiloxane having a sugar residue at a terminal or the like of a siloxane dendron structure (Patent Document 14). However, in these references, there is no disclosure of a co-modified organopolysiloxane having a modified group containing a saccharide component as a functional group independent of a siloxane dendron structure in the molecule, and there is no mention or suggestion of the performance or the like as a surface treatment agent. Further, these substances are completely different inventions from the inventions of this application in that in order to modify the siloxane dendron structure serving as the organopolysiloxane hydrophobic functional group disclosed in this reference with a hydrophilic group, it is necessary to introduce a sugar residue into a raw material intermediate by means of a multistage reaction (see paragraph 0014), which leads to the problem that the substances cannot be produced at low cost.